Preparation of esters



Patented Aug. .4, 1931 PATENT E JEROME MARTIN AND IGNAGE J. KRCH OF TEBRE HAU'IE, INDIANA, ASSIGNORS T COMMERCIAL SOLVENTS CORPORATION, 'I'ION 0F MARYLAND 0F TERRE.HAUTE, INDIANA, A CORPORA- rnnraaa'rrou or ns rnas No Drawing. Application filed ljiay 18,

' tion of an alcohol with an acid, or by alcoholysis, In the latter case, it is necessary to make use of an ester which has previously been prepared by. esterification, so it is readily seen that the former method has been basic for preparing esters.

We are aware of the fact that it has recently been claimed (English Patent 282,448) that it is possible to obtain condensation products by passing alcohols over suitable cata lysts. According to this process, however, which consists of passing an alcohol, such as ethyl'alcohol, at ordinary pressure and at a temperature of 400500- C. over catalysts such as barium oxide, magnesia, hme,-{manga-nese oxide, magnesium alcoholate, and

sodium alcoholate, there is obtained a mixture of alcohols, acids, esters, acetals, acetone, and" acetaldehyde. According to a speclfic example, when ethyl alcohol was passed over a catalyst composed of barium oxide, the products consisted of higher alcohols, such as butyl alcohol, acids, esters, such as ethyl acetate, acetals, particularly diethyl acetal, and a'lde-.

hyde. Our new process of preparing esters has very distinct advantages over. thisproc:

ess, in that we are able to obtain much higher poses, thereby reducing the operating losses to a minimum.

The formation of esters from alcohols under the influence of certain catalysts at high 1928. serial no. 278,333.

temperatures may be regarded as taking place I as follows:

2o=moH=o,H5ooo.cH3+2m zo,HD0H=c,n.ooc.c,H1+2H, C2H5OH+C4HBOH=C2H5OOC- C H1+2l1a While we do notknow the exact mechanism of the react on 1t appears that the alcohol may be first dehydrogenated into the corre sponding aldehyde two molecules of which, 7

under certain conditions, then condense to forman ester.- This theory is at least partia-l.

ly corroborated by'the fact that Tistschenko (J our. Russ. Phys. Chem. Soc. 38 ii. 355-418, 482550) found that it was possible to obtain esters such as ethyl acetate from acetaldehyde or propyl propionate from propaldehyde, by the .use of an .aluminium alkoxide catalyst. More recently, modifications of this process have been patented by Imray (British Pat- H ent 1288*1915) and Mu dan and He'rrmann (U; S. Patent 1,459,852 We have found, however, that when an aldehyde and an alcohol are passed under similar operating conditions over catalysts of the character hereinafter described, much lower yields of esters are obtained from the aldehyde than from the corresponding alcohol. W e have also found that the amount ofhigh-boiling material, other than ester, formed during the condensation process is greatly reduced by the use of an alcohol as the raw material.

As has previously been pointed out, esters can be produced from. primary alcohols, such as ethanol and butanol', bynieans of a number of different catalysts. We have now discovered a new type of catalyst quite different from any previouslyjrecommended for this purpose and which has the decided advantage of giving much larger yields of-the desired products, together with v smaller proportions of undesired products. As will be seen from the examples cited below, the composition of our new and improved catalyst may be variedcons'iderably and still give satisfactory results. Examples of a number of the catalysts which we have Table I Catalyst No. Initial composition of catalyst As will be seen from a consideration of the above table, the essential constituents of these catalysts are metallic silver or a silver compound, which under the operating conditions is probably quickly reduced to metallic silver, and a metal uranyl compound, the term metal being applied generally to metals other than uranium. The ratio of silver compound to metal uranyl compound in the catalyst may be varied within wide limits without seriously attecting their catalytic activity. The metals to be used in the metal uranyl carbonate compound may be derived from an element or elements occurring in groups I, II or IV, of Mendelejeffs periodic table. The elements which we have successfully used for this purpose include: calcium, strontium, barium, magnesium, zinc, silver, and lead.

In addition to the silver compound and metal uranyl compound, we have found it advisable to have present another compound such as a hydroxide of an element or elements occurring in groups II?) to IV inclusive, of the periodic table. (By group 116 is meant the subgroup of oup II which contains zinc, cadmium and mercury). Compounds of this type which we have successfully used are: beryllium, aluminium, thorium, and zirconium hydroxides. These metal hydroxides appear to aid chiefly in hardening the catalysts, altho there is some indication that they serve to some extent as promoters also. Even without this effect, hoWever,-a catalyst containing a metal hydroxide of the character specified lasts much longer than one not containing such a material.

A method of preparing our catalyst may be illustrated by the following example. It is distinctly understood, however, that we do not confine ourselves tothis exact method nor to the amounts of materials mentioned. One-fifth gram mol of uranyl nitrate, UO '(NO .6H O; two-fifths gram mol'of barium nitrate, Ba(NO two-fifths gram mol silver nitrate, AgNO and one-fifth gram mol aluminium nitrate; i

. Al (N0 .9H O are dissolved in four liters of distilled Wahours.

ter. To this solution is next added a solution of 160 grams of potassium carbonate, K 60 in two liters 0 Water. The resulting precipitate is then washed by decantation With distilled water until free from nitrate ions. The precipitate is filtered, pressed dry, and then slowly dried at 50 C. for 48 The dried cake thus formed is broken up to 8-14 mesh and used for the catalytlc conversion of alcohols to esters.

Instead of efi'ecting the precipitation as described above to give the carbonate form, the corresponding hydrate or phosphate, etc. compounds such as shown b catalysts A129M and A134M may be ikewise obtained. Such compositions, however, do not give as satisfactory results as when the corresponding carbonate is employed.

Another satisfactory method of preparing our catalyst is illustrated by the method followed in preparing catalyst A132M. In this case, the requisite amount of Ag O was thoroughly mixed with precipitated aluminium hydroxide and barium uranyl carbonate. Satisfactory results may also be obtained by substituting colloidal silver for the silver oxide.

A number of methods may be employed for preparing and sending the alcohol or alcohols over the catalyst. One method of accomplishing this is to force the said alcohol or alcohols over the catalyst by means of carbon dioxide or other inert gas under pressure. The liquid alcohol is in this process vaporized directly in the catalyst chamber. A sec- 0nd method of carrying out the process which we have found to be satisfactory is to bubble carbon dioxide gas thru the alcohol or alcohols which it is desired to convert, and pass the vapor thus obtained over the catalyst.

In order to effect the conversion of alcohols to esters by our new method, the alcohol or alcohols, alone or mixed with carbon dioxide or other inert gas or gases, is passed over catalysts repared as described, at temperatures pre erably from 250 to 400 C., using a pressure of preferably from. about 1 to about 200 atmospheres. While it is possible to use temperatures outside of the range specified, we have found, that, as a rule, temperatures below 250 C. give low conversions and temperatures above 400 C. give too many side reactions. -We may, however, use temperatures as low as 200 C. and as high as The table given below shows data on the conversion of ethyl alcohol to ethyl acetate under different conditions and with diflerent catalysts. In each case, 10 c. c of catalyst having the initial composition shown in Table I was used. It should be pointed out that thecatalyst mixture is composed wholly of carbonates only at the beginning of the operation. Soon after the 0 eration starts, thev silver carbonate is probably reduced to silver and it is probable that the metal uranyl carbonate is also decomposed to some extent. Part of these runs were made with ordinary 95% ethyl alcohol and part with alcohol containing 5% water and about 1% acetaldehyde.

In runs 9-1011, a mixture composed of 70% hydrogen and 30% carbon dioxide was used to force the alcohol over the catalyst. This gas mixture was also used in run #1 shown in the next table.

, The following table shows results similarly obtained with n-butyl alcohol. Runs 1 and 4 were made with 10 c. c. of catalyst, the remainder with c. c.

Table III fEsterd Pressure Rate of Run Catalyst, lbs. per 2 6 flow c. c. i sq. m. per hr. condn sate The results shown in Tables II and III above, were obtained'by one passage over the catalyst. In addition to the unconverted alcohol and the ester, there are formed also small quantities of high boiling materials, as well as small amounts of the aldehyde of the alcohol used The amounts of these high boiling materials may be kept at a minimum by conducting the reaction at as low temperatures as-is consistent with the rate of conversion and yield of the desired ester.

In the examples described above, we have only shown specific data relating to the production of ethyl acetate and butyl butyrate.

our process applies also to. the production of other similar esters such as propyl propionate, ethyl butyrate, ethyl propionate, propyl but rate, etc. h

ow having described our invention, what we claim as new and novel is It is distinctly understood, however, that- 1. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst compositions comprising initially a metal uranyl carbonate and silver carbonate. I

2. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst a composition comprising initially metal uranyl compounds and silver compounds.

3. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using a catalyst comprising metal uranyl compounds and metallic silver.

4. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst a composition comprising initially metal uranyl carbonates and silver com pounds.

5. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using a catalyst mass comprising metal uranyl carbonates and metallic silver.

6. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using a catalyst comprising a metal uranyl carbonate and metallic silver. v

7 In the process of preparing esters from primary alcohols, the step which comprises using as a catalyst compositions initially com prising barium uranyl carbonate and silver compounds.

8. In the process of preparing esters from 7 primary alcohols havingmore than one carbon atom, the step which comprises using as a catalyst compositions initially comprising barium uranyl carbonate and silver carbonate.

9. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using a catalyst comprising barium uranyl carbonate and metallic silver.

10. The process of preparing esters from primary alcohols which comprises passing said alcohols, in the vapor form, at superatmospheric pressures and at temperatures ranging from 200 to 450 (1, over compositions comprising initially, a metal uranyl compound and a silver compound. I

11. The process of preparing esters from primary alcohols which comprises passing said alcohols, in the vapor form, at superatmospheric pressures and at temperatures ranging from 200 to 450 (1, over catalysts comprising metal uranyl compounds and me-'- tallic silver.

'12. The process of preparing esters from Y .i primary alcohols which comprises passing said alcohols, in the vapor form, at superatmospheric pressures and at temperatures ranging from 200 to 450 0., over catalysts comprising metal uranyl carbonate and metallic silver.

13. The process of preparing esters from primary alcohols which comprises passing said alcohols, in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 to 450 C., over catalysts comprising a metal uranyl compound and metallic silver.

14. The process of preparing esters from primary alcohols which comprises passing said alcohols, in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 to 450 C., over catalysts comprising a metal uranyl carbonate, metallic silver, and a hydroxide of a metal found in groups II?) to IV inclusive of Mendelejeffs periodic table.

15. In the rocess of preparing esters from rimary alco ols having more than one car- 'n atom, the steps which comprise passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures g bon atom, the steps which comprise passing from 200 C. to 450 C., over compositions comprising initially. silver carbonate and uranyl carbonates of metals selected from the group consisting of calcium strontium, bar1- um, magnesium, zinc, silverand lead.

16. In the process of preparing esters from primary alcohols havingmore than onecarbon atom, the steps which \comprise passing said alcohols in'the vapor form, at pressures I from 1 to 200 atmospheres and temperatures from 200 C. to 450 C. over catalysts comprising metallic silver and uranyl carbonates f mnfalq snlantarl irnm the. grown consisting metals selected from the group consisting of aluminium, thorium, zirconium, and beryllium.

19. The process of preparing esters from primary alcohols which comprises passing said alcohols, in the vapor form, at superatmospheric pressures and at temperatures said alcohols, in the vapor form, at temperatures ranging from 200 to 450 0., over compositions comprising initially, barium uranyl carbonate, silver carbonate, and aluminium hydroxide.

22. The process of preparing esters from primary alcohols which comprises passing said alcohols, in the vapor/form, at temperatures ranging from 200 to 450 C., over catalysts comprising barium uranyl carbonate, metallic silver,- and aluminium hydroXide.

In testimony whereof we afiix our signatures. v

JEROME MARTIN. IGNACE J. KRCHMA.

of calcium, strontium, barium, magnesium,

zinc, silver and lead.

17. In the process of preparingesters from uranyl carbonates of metals selected from the group consisting of calcium, strontium, barium, magnesium. zinc, silver, and lead; and hydroxides of metals selected from the group consisting of aluminium, thorium, zirconium and beryllium.

18. In the process of preparing esters from 1 primary alcohols having more than one cars'aid alcohols, in thevapor form, at pressures from 1 to 200 atmospheres, and .at temperatures from 200 C. to 450Cr over catalysts comprising metallic silver, uranyl carbonates of metals selected from the group consisting of calcium, strontium, barium, magnesium zinc, silver, and lead; and hydroxides o 

